1. Field of the Invention
The present invention relates to remote controlled compaction machines such as trench rollers and, more particularly, relates to a compaction machine with improved remote control capabilities and to a method of operating such a machine.
2. Discussion of the Related Art
Compaction machines are used in a variety of ground compaction and ground leveling applications. Most compaction machines have supports in the form of plates or rollers that rest on the surface to be compacted, and most of these supports are excited to vibrate so as to compact and level a worked surface. These machines are commonly referred to as “vibratory compactors.”
A common vibratory compactor, and one to which the invention is well-suited, is a vibratory trench roller. The typical vibratory trench roller includes a chassis supported on the surface to be compacted by front and rear rotating drum assemblies. Each drum assembly supports a respective subframe of the chassis. In the case of an articulated trench roller, the subframes are coupled to one another by a pivot connection. Each of the drum assemblies may include a stationary axle housing and a drum that is mounted on the axle housing and that is driven to rotate by a dedicated hydraulic motor. Hydraulic motors are typically supplied with pressurized hydraulic fluid from a pump which may be powered by an engine mounted on one of the subframes.
Each drum may be excited to vibrate by a dedicated exciter assembly that is located within the associated subframe and is powered by a motor connected to a pump. Each exciter assembly typically comprises one or more eccentric masses mounted on a rotatable shaft positioned within the subframe. Rotation of the eccentric shaft imparts vibrations to the subframe and to the remainder of the drum assembly. The entire machine may be configured to be as narrow as possible so as to permit the machine to fit within a trench whose floor is to be compacted. Machine widths of less than 3 feet (1 meter) are common. Vibratory trench rollers of this basic type are disclosed, e.g., in U.S. Pat. No. 4,732,507 to Artzberger; U.S. Pat. No. 4,793,735 to Paukert; U.S. Pat. No. 5,082,396 to Polacek; U.S. Pat. No. 7,059,802 to Geier et al.; and U.S. Pat. No. 8,585,317 to Sina, the entireties of which are hereby expressly incorporated by reference thereto.
Vibratory trench rollers often are controlled remotely using a transmitter on a remote controller that transmits infrared (IR) or other signals to the trench roller on a line-of-sight basis. The control signal is generated by manipulation of a joystick and/or other controls on the remote controller and controls operation of the machine. The IR signal is received by a receiver in the form of a photodetector or “eye” on the machine, causing the machine to stop or start travel in the desired direction (forward or reverse) and/or to control the machine's exciter assemblies. Two a signals may be transmitted simultaneously, namely, a relatively high-intensity control signal having a range of on the order of 50-65 feet (15-20 meters) and a relatively low intensity safety signal having a range of about 6.6 feet (2 meters). The safety signal is generated whenever the remote controller is active and causes the machine to cease moving upon receipt of the safety signal. The machine thus stops moving if the operator is located in a “safety zone” that is typically within about 6.6 feet (2 meters) of to the machine.
Trench rollers often are used in trenches having reinforced side walls. For example, referring to FIG. 1, a vibratory trench roller or “machine” 10 may be used to compact the floor 14 of a trench 12. The reinforcement or “trench shoring” often takes the form of vertical reinforcing sheets or walls 16 located along each side wall of the trench 12 and a number of spaced cross supports 18 extending laterally between the side walls near the top edge 20 of the trench 12. The machine 10 typically is controlled by an operator stationed above the trench 12 via a hand-held remote controller 22. The remote controller 22 transmits an IR signal 24 that propagates in an expanding arc until it impinges on the machine 10, where it is detected by one of two eyes 26 and 28 located on opposite ends of the machine 10. Each eye 26 or 28 faces to the rear or front of the machine 10 and often cannot receive signals from an operator standing beyond the opposite end of the machine. Thus, each eye 26 or 28 can be considered to be associated with its own dedicated “reception zone.” This means that, under many operating conditions, only one eye 26 or 28 can receive signals 24 from the remote controller 22 at any given time.
Being located between the remote controller 22 and the machine 10, the cross supports 18 can block a portion of the signals 24, creating a “dead zone” formed by a “shadow” located downstream of the cross support 18 in the direction of IR signal propagation. The dead zone is bordered by the line 30 in FIG. 1. The machine 10 shuts down when the operative eye (rear eye 28 in the illustrated example) is positioned in the dead zone and experiences loss of signal, requiring the operator to reposition the remote controller 22 to a location in which signal receipt by the eye 28 can be reestablished. The need to reposition can be irksome to the operator, particularly if he or she is positioned on another machine, such as an excavator, and either has to move the machine or climb down off from it to reposition the remote controller 22.
The need therefore has arisen to provide a remote-control-operated vibratory trench roller or other compaction machine that does not experience loss of signal when the machine passes beneath or behind an obstruction such as a cross support of a shored trench.
The need additionally has arisen to provide a method of operating such a compaction machine.